1. Field of the Invention
This invention relates to resinous electrodepositable compositions which deposit on the cathode. More particularly, this invention relates to amine acid salt-containing resins prepared from polyepoxides.
2. Brief Description of the Prior Art
Cationic electrodepositable resinous compositions are known in the art. Thus, for example, U.S. Pat. No. 3,617,458 to Brockman discloses crosslinkable coating compositions which electrodeposit on the cathode. The coating compositions are derived from an unsaturated polymer containing amine groups and carboxylic acid groups and an epoxidized material. The compositions of Brockman differ from those of the present invention in that Brockman does not react the amine group with the epoxy group as is required by the present invention. Rather, in Brockman, the epoxy groups present are apparently esterified by the carboxyl groups, with the amine being subsequently acid-solubilized.
U.S. Pat. No. 3,663,389 to Koral et al discloses cationic electrodepositable compositions which are admixtures of certain aminealdehyde condensates and a variety of cationic resinous materials, one of which may be formed by reacting an organic polyepoxide with a secondary amine and solubilizing with acid. Notably missing from this reference is any teaching on chain extending the polyepoxides with organic polyols as is required by the present invention.
U.S. Pat. No. 3,640,926 to Slater et al discloses aqueous dispersions which electrodeposit on the cathode comprising an epoxy resin ester, water and a tertiary amine acid salt. The epoxy resin ester is the reaction product of a glycidyl polyether and a monobasic unsaturated oil acid and the amine salt is the reaction product of an aliphatic carboxylic acid with a tertiary amine. This reference differs from the present invention in that it lacks any disclosure on chain extending the polyepoxides with polyols as is required by the present invention. In fact, the epoxy esters of Slater et al contain no free epoxy groups indicating that esterification is stoichiometric leaving no opportunity for subsequent chain extension.